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BACK EMF DETECTION DURING PWM ON TIME BY ST7MC

5 APPENDIX

Following code will be put in the commutation interrupt routine MTC_C_D_IT.

if (MCPUH < threshold_duty)

// if D< threshold_duty , sample at PWM off time.

{

SET_MTC_PAGE(1);

MCONF = mem_MCONF;

SET_MTC_PAGE(0);

MCRC = mem_MCRC;

PEDDR = 0x00;

//PE7 to PE4 floating Input.

PEOR = 0x00;

//PE3 to PE0 floating Input.

}

else

// if D> threshold_duty, sample at PWM on time.

{

SET_MTC_PAGE(1);

MCONF = mem_MCONF_ontime;

SET_MTC_PAGE(0);

MCRC = mem_MCRC_ontime_HF;

PEDDR = 0x0F;

//PE7 to PE4 floating Input

PEOR = 0x0F;

//PE3 to PE0 push pull output

PEDR = 0;

//PE1,2,3=0

}

In the head file MTC_Settings_Sensorless.h, some variables are defined as:

#define mem_MCONF

((u8)2)

// Sample during PWM off time

#define mem_MCONF_ontime ((u8)162)

// Sampling during PWM on time, 25us delay

#define mem_MCRC

((u8)67)

// Internal voltage reference

#define mem_MCRC_ontime_HF((u8)79)

// External reference voltage, Z sampled at high frequency

#define threshold_duty

((u8)16)

// at fs=18.1k, T=883, this number corresponds to

around 60%